Fluid proportioners include dispensing systems that receive separate inert fluid components, mix the components in a predetermined ratio, and then dispense the mixed components as an activated compound. For example, fluid proportioners can be used to dispense epoxies and polyurethanes that solidify after mixing of a resin component and an activating material, which are individually inert. However, after mixing an immediate chemical reaction begins taking place that results in the cross-linking, curing, and solidification of the mixture. Therefore, the two components are routed separately into the proportioner so that they can remain separate as long as possible. A sprayer receives and mixes the components so the mixture can be dispensed from the sprayer.
A typical fluid proportioner includes a pair of positive displacement pumps that individually draw in fluid from separate fluid hoppers and pump pressurized fluids to the mix manifold. The pumps are driven synchronously by a common motor, typically an air motor or hydraulic motor, having a reciprocating drive shaft. Such configurations are simple and easy to design when the fluid components are dispensed in a 1:1 ratio and the pumps are of equal volumetric displacement.
Many two component epoxies and polyurethanes are not comprised of a 1:1 ratio of the components. Often, a first major component is required in a higher proportion than a second minor component. In such a case, displacement of one pump is required to be larger than the other, which can complicate the design and operation of the fluid proportioner.